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Congratulations on your choice of the MFJ-9420 20-Meter
transceiver.  The MFJ-9420 is specially designed to deliver
performance you never thought possible from a low power radio.
Please read this manual carefully before attempting to operate
your new radio.

FEATURES

The MFJ-9420 is an 

easy-to-operate

,"back to basics" radio.  Operate the unit with ease in minutes!

Quiet DBM front end and lots of overall gain for 

great sensitivity

.  If the signal is there, you'll hear it!

Adjust the tuner or aim the beam with pin-point accuracy.  A calibrated 

analog S meter

 measures even the

smallest variations in signal strength.  The meter also monitors your speech processing level on transmit.

Sharp ladder filter cuts adjacent chatter and focuses transmitter power where you need it most for 

great

selectivity

.

Effortless tuning with custom manufactured 8:1 reduction drive ball bearing VFO tuning capacitor provides
smooth and 

stable VFO

.

Big audio and 

powerful AF output

 even in noisy locations from a special Philips BTL audio chip and

rugged 3" speaker.

Full time RF speech processing 

commands speech cuts through QRM and competes with radios running

far more power.  Compare with your 100-watt rig.  You'll be amazed by the signal reports!

Packs the same punch as 50-Watt radios without the heavy 10 Amp power supply!  Designed to run on
NiCd's or the 

ultra light

 MFJ 4110 ac wall adapter supply.

Rugged Motorola PA transmitter runs cool, and tolerates 3:1 VSWR accidentally opened feedlines or
feedline shorts.

Conservative design, with a premium plate through pc board, quality components, handsome brushed
aluminum panel, and a tough vinyl clad case ensure years of dependable service.

Available 

CW adapter board

 installs and lets you jump

to the low end to work CW.

Semi-break in keying and sidetone.

At home or on the go, you'll enjoy countless hours operating the MFJ-9420.  Best of all, it's fully backed by
MFJ's exclusive "No Matter What" 1 year guarantee.  If it breaks, we'll take care of it!

You'll need three things to get your MFJ-9420 on the air fast:

12 14 Volt 2 Amp Power Source.
600 Ohm Dynamic PTT Microphone
20 Meter Antenna

1.  POWER SUPPLY:  The MFJ 4114 AC/NiCd Portable Power Pack or
MFJ-4110 ac Wall adapter.  Supply are specially designed to run
the MFJ-9420.  You may also use any 13.8 Volt supply or 10-cell
NiCd pack as long as it delivers 2 A on peaks (12 Volt supplies
will work fine but at reduced RF output).  Use a 5.5mm OD x

Содержание MFJ-9420

Страница 1: ... competes with radios running far more power Compare with your 100 watt rig You ll be amazed by the signal reports Packs the same punch as 50 Watt radios without the heavy 10 Amp power supply Designed to run on NiCd s or the ultra light MFJ 4110 ac wall adapter supply Rugged Motorola PA transmitter runs cool and tolerates 3 1 VSWR accidentally opened feedlines or feedline shorts Conservative desig...

Страница 2: ...you may find it necessary to turn down the mic gain control a screwdriver adjustment located on back panel to reduce background noise The MFJ 9420 uses an analog VFO tuning dial which is inherently less accurate than digital readouts on the plus side analog tuning reduces phase noise lowers power consumption and saves you money Please take the potential for dial error into account when operating n...

Страница 3: ...ates in single ended class AB with bias generated by clamping diode D10 T5 matches PA output to a 50 Ohm system and low pass filter L7 L8 suppresses harmonic content Level detector D9 tracks the SSB speech envelope and generates feedback to Q3 Q4 and U2 Syllabic compression of the speech waveform optimizes average transmitter output power The MFJ 9420 is especially designed to operate from light w...

Страница 4: ...s with a VSWR of 3 1 or less Use your regular station antenna or a portable 20 Meter dipole such as the MFJ 1772 ultra light For non resonant wires use a tuner such as the MFJ 971 Always rough tune for maximum receiver sensitivity first using incoming signals and your S Meter to find a peak AVOID OPERATING INTO UNMATCHED HIGH VSWR ANTENNAS THE MFJ 9420 DOES NOT HAVE A HIGH VSWR SHUT DOWN CIRCUIT A...

Страница 5: ...irectivity MFJ 1772 PORTABLE DIPOLE As an alternative to making a coax fed dipole consider purchasing the pre assembled MFJ 1772 antenna This is a no compromise 20 Meter folded dipole complete with 30 of feedline all made from ultra light weight 300 Ohm twinlead Connect a random length of coax from the MFJ 1772 feedline to your rig and let the antenna s built in 50 Ohm matching network do the rest...

Страница 6: ...adios If your antenna is good most stations won t even know you are running low power US AT 800 647 TECH 800 647 8324 Your MFJ 9420 is fully backed for 1 year by MFJ s NO MATTER WHAT GUARANTEE After that MFJ Customer Service Technicians will be there to help you keep your rig in top shape for as long as you own it However before you call us please check through this list just to make sure the prob...

Страница 7: ...hm Resistive Dummy Load 14 MHZ Signal Generator or other weak signal source General Coverage Receiver with digital readout INITIAL TEST SET UP A Remove transceiver cover B Connect 13 8 Volts Power Supply to Power Jack C Connect Microphone D Turn on unit VOLTAGE CHECKS AND ADJUSTMENTS use voltmeter A VOLTAGE REGULATOR Set R64 for 10 0 V at TP1 B RECEIVER AGC Set R6 for 4 3 Volts at TP2 VFO CALIBRAT...

Страница 8: ...O Carrier osc freq VFO CAL VFO freq adj IF1 IF2 IF ampl peak L1 L2 RX front end peak L5 L6 TX filter peak CAR BAL T3 Carrier null PA BIAS PA idle current SP PROC TX ALC level MIC GAIN TX audio level TUNE SW Full carrier out PWR Power on VOL AF Ampl gain control VFO TUNE Sets operating freq FUSE Reverse polarity protect If reverse polarity track fuse opens install a miniature 2 5 A pigtail fuse or ...

Страница 9: ...T mode Test with TUNE switch depressed DO NOT TEST gate of Q9 may cause generation of parasitic oscillations Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 D E 9 8 0 9 0 9 7 0 0 3 5 0 13 0 0 25 S B 2 3 0 7 3 9 8 9 0 7 0 7 2 8 0 0 1 0 G C 0 13 2 0 4 3 13 0 0 0 9 0 13 7 Q11 MRF477 PA Transistor To avoid RF damage to DVM check collector voltage in receive mode only full supply voltage 13 8v should be present Check b...

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